With rapid growth of electronic terminal equipment in recent years, the electronic terminal equipment is downsized, made thinner and becomes high performance. A semiconductor device mounted in the electronic terminal equipment is downsized and densified in association with this, and flip-chip mounting is rapidly spread as a method of mounting a semiconductor chip (hereinafter, may be referred to as a chip) on a circuit board (hereinafter, may be referred to as a board).
In order to enhance reliability of the semiconductor device, an underfill material is filled in a gap between the chip and the board. As a method of filling the underfill material, a method of filling the underfill material in a gap between the chip and the board by use of a capillary phenomenon is common; however, there are problems that an unfilled state easily occurs and production cost is high. As a technique for solving these problems, a technique of forming an underfill material on a wafer and bonding a singulated semiconductor chip to a board is contrived. A method of forming an underfill material on a wafer includes a method of forming a resin composition formed into a film on a wafer through vacuum thermally laminating treatment or the like, and a method of directly applying a resin coating material to form on a wafer.
Although an epoxy resin is commonly used for the underfill material for providing adhesiveness, difference in a coefficient of linear expansion with a chip to be bonded is large if using only an epoxy resin. Therefore, it is difficult to maintain connection reliability when the semiconductor device is subjected to a treatment involving large changes in temperature and requiring higher durability, such as a moisture absorption/reflow treatment and a thermal cycle treatment. Accordingly, inorganic particles may be mixed in large amounts in the underfill material for the purpose of reducing the difference in a coefficient of linear expansion with a chip.
On the other hand, there are a technology of mixing a polyimide for the purpose of imparting heat resistance to the underfill material (refer to Patent Document 1) and a technology of mixing rubber particles for the purpose of relaxing stress exerted on a cured underfill material (refer to Patent Document 2).